1.1: toluene-4-sulfonic acid / methanol / 1 h / 25 °C 2.1: trichlorophosphate / toluene / 0.17 h / 20 °C / Inert atmosphere 2.2: 3 h / 30 - 75 °C 3.1: isopropyl alcohol / 4 h / 70 °C / Inert atmosphere 4.1: sodium hydroxide / ethyl acetate; water / pH ~ 10 / Inert atmosphere 4.2: 1 h / 40 °C View Scheme